The present invention relates to a wire cut electric discharge machine and, more particularly, to an automatic connecting apparatus for a wire electrode.
A wire cut electric discharge machine has been known, which comprises upper and lower wire guides respectively arranged above and below a workpiece table for supporting a workpiece, a wire feed mechanism for feeding the wire electrode downward while clamping it, and a wire recovery device arranged below the lower wire guide. In this conventional electric discharge machine, during electric discharge machining, the wire electrode is continuously fed downward by the wire feed mechanism, and is guided to the wire recovery device via wire paths defined in the wire guides. When the electric discharge machining position of the workpiece is to be changed, the wire electrode must be temporarily cut and must be automatically extended between the wire guides. When the wire electrode is broken in the electric discharge machining region, it is required to draw the broken wire electrode upward from the electric discharge machining region, and then cut a bent portion or a portion with a roughened surface of the wire electrode, and thereafter effect automatic extension of the wire electrode. For this reason, a wire cutting device is conventionally arranged above or below the upper wire guide.
In case that the wire cutting device is arranged above the upper wire guide, the used portion of the wire electrode which is cut from the remaining portion thereof by the wire cutting device is fed downward upon operation of the wire feed mechanism. At this time, the cut end of the wire electrode is easily caught in narrow wire paths of the wire guides and a hole or groove of the workpiece, and thus it is difficult to reliably perform an automatic extension operation of the wire electrode. Even if the wire cutting device is arranged below the upper wire guide, it is also difficult to smoothly pass the wire electrode through the hole or groove of the workpiece and the narrow wire path of the lower wire guide.